I have a question about low salinity. I have a FO tank without inverts. My first fish are two percula clowns. They are in my quarentine tank with low salinity at 1.008. They've been in there for three weeks now and they are not showing any signs of stress nor disease. They are also eating like pigs. I've heard that marine fish greatly benefit from low salinity by being much less stressed due to better osmotic control and are not likely to be affected by diseases, since marine parasites and diseases are intolerant of low salinity. I'm wondering if I can adjust my salinity to 1.008 in my main tank and leave it there for good. Any advice would be greatly appreciated.

i agree with 1.025, although i do keep my tanks around 1.021. i think that 1.008 is probably too low- i personally wouldnt lower my salinity any lower than 1.014, even for theraputic purposes. in the short term you may not see adverse affects, but in the long term there may be.

Fish have evolved over millions of years to live within a certain range. The idea of keeping them out of range has been around for less than a couple decades. Darwin's theory says the last couple decades can go get stuffed, and not with good things like cheese and beer.

But really, the theory gained popularity not too long ago and generally a range of .019 to .020 is considered low salinity for this purpose. .008 is really low. The theory has also been debunked on numerous ocaisions. While the fish may seem fine for short term, they are in reality drowning slowly.

Fish, both saltwater and fresh maintain osmostic balance by adapting to the surrounding water. Saltwater fish take in a massive amount of water at any given time because their body is constantly trying to disolve and absorb the salt surrounding them. They do this by releasing water through their skin to disolve the salt. Freshwater fish maintain balance by taking in relatively little water. Put a fw fish in salt and it dies by dehydration as it releases all of it's water to try and disolve the salt around it. Put a sw fish in fresh and it drowns because it continues to pull in water, but not expel it through it's skin. Remember, this is happening at a cellular level and is nothing that can be controlled by the fish.

I have researched the subject of hyposaline conditions and reef fish as completely as anyone. I have to disagree with some of the points here. To start with there is evidence that fish actually evolved in a much less saline environment than modern reefs. I also disagree that the value of hyposalinity as a therapy has been debunked at all. A salinity (not SG) of 16ppt or lower has been proven to be effective for treating Cryptocaryon irritans (ich). A specific gravity of 1.014 is far too high to treat ich. There are numerous studies in the scientific journals that prove that marine teleost fish not only tolerate such a low salinity they appear to thrive in it. The use of hyposaline conditions is a commonly used practice in commercial fisheries to relieve the stress of transport and handling and it greatly increases the survival rate of badly stressed marine fish.

I don‚Äôt mean to be disagreeable, but the description in another post of the osmoregulatory process is erroneous. Having said all of this, I do not recommend keeping fish in hyposaline conditions on a permanent basis, only as a therapy (months at a time are even safe). Here is a link were you can find some references on the subject of the adaptability of marine fish to hyposaline conditions:http://www.marineaquariumadvice.com/...um_fish_5.html

terryB, I'm not disputing the use of hyposalinity in quarantine or therapy and have used FW dips in the past. I'm refering to the long term environment and the advice of some to keep fish permanently in low saline condtions. I've not found anything in my readings which gives any real benefit to it and generally everything I've found has stated the risk outweighs the possible benefits. For my purposes it is not an option as I keep inverts. But even for FO I would only see it as an option for short term.

For my own personal experience with ICH I've had poor long term performance from hypo and FW dips and had complete success with garlic and vitamins. The 2 fish I treated with dips did not survive the outbreak. The 2 I treated with garlic while in the infested display tank survived with no ill effects and have not had an outbreak since. As I did not treat the display tank with any meds I believe the 2 survivors developed immunity quickly.